﻿<p>A building system is a group by which building elements are grouped according to a common function within the building.</p>
<p>The group <em>IfcBuildingSystem</em> defines the occurrence of a specialized system for use within the context of a building and
finishing fabric. Important functionalities for the description of a building system are derived from supertypes:</p>
<ul>
<li>From <em>IfcSystem</em> it inherits the ability to couple the building system via <em>IfcRelServicesBuildings</em> to one or more
<em>IfcSpatialElement</em> subtypes as necessary.</li> 
<li>From <em>IfcGroup</em> it inherits the inverse attribute <em>IsGroupedBy</em>, pointing to the relationship class
<em>IfcRelAssignsToGroup</em>. This allows to group building elements (instances of <em>IfcBuildingElement</em> subtypes,
<em>IfcFurnishingElement</em> subtype, <em>IfcElementAssembly</em> and <em>IfcTransportElement</em>).</li>
<li>From <em>IfcObjectDefinition</em> it inherits the inverse attribute <em>IsDecomposedBy</em> pointing to the relationship
class <em>IfcRelAggregates</em>. It provides the hierarchy between the separate (partial) building systems.</li>
</ul>

<blockquote class="history">
HISTORY&nbsp; New entity in IFC4.
</blockquote>
